Coronaviruses are a group of enveloped, RNA-containing viruses which cause serious diseases of domestic and laboratory animals including respiratory infections, diarrhea, wasting disease, hepatitis, encephalitis, and demyelinating neurological disease. In man, coronaviruses cause more than 30% of colds. Because of the difficulty of coronavirus isolation and the lack of sensitive serological tests for human coronaviruses, the role that these viruses may play in acute disease such as diarrhea and chronic disease wuch as neurological diseases is yet not known. Recent biochemical studies of coronaviruses in our laboratory and others have shown that coronaviruses have a unique replication strategy and that properties of the two glycoproteins, E1 and E2, may be responsible for some of the special features of coronavirus replication. The E2 glycoprotein which forms the peplomers of the viral envelope, has N-linked oligosaccharides like all other viral glycoproteins, whereas the E1 glycoprotein of the viral membrane appears to ave 0-linked oligosaccharides. These viral polypeptides can be used as model systems to compare the cellular mechanisms used to synthesize, process, and transport N- and 0-linked cellular glycoproteins. For each of the glycoproteins we will elucidate the synthesis, insertion into membranes, mechanisms of glycosylation, intracellular transport, and assembly into the viral envelope, using an invitro translation system and by cell fractionation techniques. We will analyze the functions of E1 and E2 using liposomal model systems, monoclonal antibodies and viral mutants. These studies will demonstrate the role of E1 and E2 in virus envelope formation, release of virions from infected cells, interaction with receptors, elicitation of cellular and humoral immune responses, and induction of cell fusion. The fundamental information on coronavirus replication provided by these studies will have applications to the development of methods to isolate coronaviruses and to detect coronavirus infections.